The present invention generally relates to an image forming system and, more particularly, to an image forming system related to a printer system such as a laser beam printer, a light-emitting device (LED) printer, a liquid crystal shutter printer or an ink jet printer, or related to a high performance copier or a high performance facsimile machine.
Recently, an image forming apparatus has been formed as "a system". Generally, an image forming system such as a laser beam printer system is made up of a mainframe of the system (system mainframe), and various optional units which are detachably attached to the system mainframe. A system mainframe receives character code information or image information supplied from a host system coupled to the image forming system, and forms an image on a recording medium. A word processor, an office computer or a personal computer may be used as a host system. Another type of the system mainframe is known which directly receives image information from a host system. In this case, the image forming function is provided in the host system. Optional units are coupled to the system mainframe through respective interfaces. Those examples of optional units are a recording medium feed unit such as a large-capacity paper feed unit or a multi-tray (cassette) paper feed unit, a recording medium transporting unit such as a paper transporting unit for use in duplex print, and a recording medium eject unit such as a large-capacity paper eject unit or a multi-tray (cassette) paper eject unit.
However, in conventional image forming systems, a problem occurs when a host system or an image processing device inquires status of an image forming device (print engine) or an optional unit. That is, in a case where a plurality of pieces of information exist, only one piece of information having the highest priority is sent back to the host system or the image processing device.
Additionally, in conventional image forming systems, the host system or the image processing device must issue different commands having different contents in order to obtain a variety of status or numerical information relating to the image forming device.